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So, a recent discussion on M1 Garand-specific ammo got me thinking about gas operating systems in firearms. The reason I had been told that Garands either needed specific ammo or an adjustable gas plug to avoid damaging their op rods was because modern ammo used powders optimized for heavier bullets in longer barrels, i.e. a slower burn rate. This, it was said, maintained higher barrel pressures for a longer time, putting more stress on the Garand's gas system than it was designed for.


And that made sense to me. I don't know much about internal ballistics, but spreading the pressure out seemed like a reasonable way to launch heavier projectiles without greatly increasing chamber pressure. That would also mean that the gas piston could be under more pressure for longer than it would be when using M2 ball. Garands, after all, use a long-stroke gas system. Other rifles, like the AK, would be less sensitive to this since they use short-stroke gas systems.


Or do they? Several sources of varying authoritativeness seem to think AKs use a long-stroke system because the piston is attached to the bolt carrier and reciprocates the entire length of the carrier's travel. My understanding, however, is that the length of stroke is related to the length of travel that the piston makes while under the pressure of the expanding propellant gasses. It was somehow related to the diameter of the piston. For example, if the piston traveled under pressure for a distance of more than the piston diameter, then it was long-stroke, much like an engine with a stroke ratio greater than 1 is considered "long-stroke".


Oddly, the most authoritative source I found on the subject, an article from American Rfileman is the only one that confirmed my preconception, but it fails to elaborate on the differences between the two designs. So, I guess that's what I'm asking you guys. Is a long-stroke gas system any gas system where the piston is stuck to the bolt carrier?

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on a short stroke the piston moves freely from the bolt, like on my rfb. If the piston is attached to the bolt like on my saiga, its a long stroke.


and oddly, the article you posted starts out on a bad note. Stoner did design tthe AR, but jt was the AR 10. Fremont and sullivan made the ar15 under army contract based on the ar10 design. Stoner had nothing to do with the DGI system on the ar15 which became the m16.


I hate thping in this damn kindle!x

Edited by Stryker0946
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Just to differentiate between an online magazine article from a national firearms organization and some guy on the Internet, do you have a source on that? I ask because I've been playing around with my search terms and am finding some more guys on the Internet who say differently.


As for the other nitpicking with the article, my understanding is that Stoner was Armalite's chief engineer and that Freemont and Sullivan were his underlings (National Firearm Museum). Far from bunkum, if the AR-15 were to be called anything other than Stoner's design, there would be cries of despair that it was stolen from him.

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